The subject matter disclosed herein relates to a system for detecting generator winding faults.
Certain wind turbines include a double-fed induction generator (DFIG) to convert wind energy into electrical energy. As blades of the wind turbine rotate, the blades drive a rotor to rotate with respect to a stator, thereby producing electrical energy. DFIGs are generally electrically coupled to a converter that regulates a flow of electrical power between the DFIG and an electrical grid. Specifically, the converter enables the wind turbine to output electrical power at the grid frequency regardless of the rotational speed of the wind turbine blades.
Induction generators in general, and DFIGs in particular, include wire windings within the rotor and the stator. In operation, a rotating magnetic field is established between these windings, thereby inducing an output electric current. Unfortunately, the windings of the rotor and/or the stator may be exposed to high current loads (i.e., greater than design loads) during operation. Such high currents may degrade the insulation between windings, thereby forming a turn fault (i.e., short between windings), or a ground fault (i.e., short between one or more windings and an electrical ground). Such winding faults may decrease the efficiency of the DFIG. Therefore, inspection and maintenance of the DFIG may be performed at regular intervals to mitigate this loss in efficiency. A typical inspection technique involves manually measuring the resistance of each winding within the rotor and the stator using a micro-ohm meter. Such an operation generally requires an operator to climb the wind turbine tower, enter the nacelle, and connect the micro-ohm meter to the DFIG. Because this procedure is both expensive and time-consuming, it is generally performed at longer than desired time intervals. Consequently, wind turbines may operate in an inefficient manner for significant periods. In addition, the micro-ohm meter may fail to identify winding faults in certain cases.